Page 587 - Dynamics of Mechanical Systems

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568 Dynamics of Mechanical Systems

16.15 Closure
This concludes our relatively brief introduction to cams and to cam–follower pairs.
Although we have focused our attention upon two-dimensional movements, the same
principles may readily be applied with cams and followers moving in three dimensions.
The difference is simply geometry. The kinematic principles are the same.
A principal concern in cam and follower design is that unwanted accelerations and jerks
may be generated. These accelerations and jerks may then produce unwanted and harmful
forces, especially with high-speed systems. In the immediate foregoing sections, we have
considered various follower rise functions and their effects upon the follower acceleration
and jerk. We have seen that the cycloidal function reduces the jerk but at the cost of slightly
higher acceleration.
Another way of alleviating the effects of large acceleration and jerk is to use large cams.
The disadvantage of large cams, of course, is that they may not be practical for use with
small and compact machines. Still another concern in cam–follower design is that the
pressure angle between the cam and follower should be kept as small as possible to reduce
contact forces.
Finally, for efficient and relatively low-stress cam–follower systems, it is important that
precision manufacturing be used to ensure adherence to the desired design geometry.
Also, regular maintenance and inspection are essential for long wear and long-lived
systems. Readers interested in more advanced aspects of cam–follower design may wish
to consult the references.
In the following chapter, we consider gears, another widely used component in machine
design. A gear tooth may be viewed as a specialized cam.

References

16.1. Paul, B., Kinematics and Dynamics of Planar Machinery, Prentice Hall, Englewood Cliffs, NJ,
1979, chap. 4.
16.2. Graustein, W. C., Differential Geometry, Dover, New York, 1962, pp. 64–67.
16.3. Davis, S. A., Feedback and Control Systems, rev. ed., Simon & Schuster Technical Outlines,
New York, 1974, pp. 44–46.
16.4. Tuma, J. J., Engineering Mathematics Handbook, 2nd ed., McGraw-Hill, New York, 1979,
p. 230.
16.5. Butkov, E., Mathematical Physics, Addison-Wesley, Reading, MA, 1968, chap. 6.
16.6. Roark, R. J., and Young, W. C., Formulas for Stress and Strain, 5th ed., McGraw-Hill, New
York, 1975, pp. 11, 94.
16.7. Oberg, E., Jones, F. D., and Horton, H. L., in Machinery’s Handbook, 23rd ed., Ryftel, H. H.,
Ed., Industrial Press, New York, 988, pp. 2049–2075.
16.8. Erdman, A. G., and Sandov, G. N., Mechanism Design: Analysis and Synthesis, Vol. I, 2nd
ed., Prentice Hall, Englewood Cliffs, NJ, 1984, chap. 6.
16.9. Wilson, C. F., Sadler, J. P., and Michels, W. J., Kinematics and Dynamics of Machinery, Harper
& Row, New York, 1983, chap. 5.